Yeah - really shouldn't be that hard - above each channel strip you will see a section labeled FX with a button labelled 1 & 2 - these correspond to to the effects units 1 & 2 on either side of the S4 - simple really - but RTFM x `100000000000000000

And perhaps get used to the basics of actually playing the music well before you go crazy on FX

Catch me @ Miss Marley's in Manly on the weekends for quality tunes and amazing tequila!